The present invention relates to a battery module formed by one or more rechargeable batteries and an assembled battery formed by battery modules.
Nickel-metal hydride rechargeable batteries and lithium-ion rechargeable batteries, which have high energy density, are used as conventional on-vehicle power supplies for electric cars, hybrid cars, and the like. Such a rechargeable battery is normally an assembled battery. The assembled battery is formed, for example, by combining battery modules. Each battery module includes one or more battery cells and a rectangular resin case that accommodates the battery cells.
When a battery cell is charged or discharged, the temperature of the battery cell increases. This adversely affects the properties of the battery cell. Accordingly, an increase in the temperature of the battery cells in a battery module adversely affects the properties of the assembled battery. The battery modules may be air-cooled to limit such increases in the temperature of the battery cells and sustain the properties of the assembled battery. Japanese Laid-Open Patent Publication No. 2006-156049 describes one example of a structure for cooling battery modules that form an assembled battery.
Japanese Laid-Open Patent Publication No. 2006-156049 describes a battery case for a rechargeable battery that includes an irregularity wall. The irregularity wall includes ridges and valleys that extend in a height-wise direction of the battery and are alternately arranged in a width-wise direction of the battery. Each ridge includes contact portions that contact another battery case when the battery cases are in contact with each other. Each valley includes an inner wall having a flat surface and an outer wall having a groove that extends in the battery height-wise direction. The groove has the form of an arc bulging inwardly into the battery case in a cross-sectional view taken in a direction orthogonal to the battery height-wise direction.